Steve Ghertner and Patrick Becker from the Middle Tennessee Robotic Arts Society (MTRAS) recently hosted a line following robot contest as part of “Engineering Day” at the Adventure Science Center in Nashville, Tenn. It was planned to be a basic course of black tape on white board and the kids to build the bot that could finish the course the fastest would win some nice prizes. That sounds fun but what could make it more interesting?
The guys had recently seen the Plotclock project that had made its rounds on the internet and were intrigued. The original design is a servo-controlled, hinged arm plotter that uses a dry erase marker to write out the time on a mini whiteboard every minute. At the start of the next minute, it erases the previous time and writes the new time. A very cool bot! But Steve and Patrick had a different application in mind.
Since they needed a timer for the races and stopwatches are very non-robotic (and boring!), they saw the Plotclock as a starting point for a very cool solution. The idea was simple – add an ultrasonic rangefinder and use it to detect when the robot left the starting line and when it reached the finish line. An Arduino would calculate the time between start and stop and send the elapsed time to the Plotclock and have it jot down the time on a Post-It note for the contestant to keep.
With this plan they went into action and in a weekend day, Patrick cut out all the parts on his laser cutter while Steve cranked out some Arduino code for the Diecimila. They also added an Adafruit LCD shield for good measure. The timer bot works great. Instead of using a dry erase marker as in the original design, they gave the bot a pencil after finding that felt tipped markers were drying out too quickly. They’ve released their source code for all to enjoy.
What other alternate uses do you have for the Plotclock? Leave them in the comments below.